Tutorial

In this page is explained how to build an AppImage for a simple Qt/Qml application. The tutorial is meant to be performed in a Ubuntu (18.04 or newer) system where appimage-builder have been installed. Check the Get appimage-builder for instructions. The application code can be found here.

Compiling the sources

The first step in our process is to build the application binaries. We will set the install prefix to ‘/usr’ as appimage-builder expects to find the application resources (desktop entry and the icon) in their standard paths.

# install build dependencies
sudo apt-get install git cmake zlib1g-dev qtdeclarative5-dev qml-module-qtquick2 qml-module-qtquick-window2 qml-module-qtquick-layouts qml-module-qtquick-layouts qml-module-qtquick-controls2

# get the application source code
git clone https://www.opencode.net/azubieta/qt-appimage-template.git

# step into the application source code dir
cd qt-appimage-template

# configure the build in 'release' mode using '/usr' as prefix
cmake . -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr

# compile the application
make

Preparing the AppDir

We will use the DESTDIR make variable to install the binaries using a root different than ‘/’. Notice that while many build toolchains such as cmake support this variable it’s not standard.

# install the application to 'AppDir'
make install DESTDIR=AppDir

After installing the application into the AppDir we need to verify that it works as expected. Therefore we will execute it and manually check that the application windows shows and all the components are visible and functional.

If the application fails to run or doesn’t shows a window when executed you will need to investigate and solve the issue before continuing. Notice that applications must be relocatable in order to be put inside and AppImage.

# execute the application
AppDir/usr/bin/appimage-demo-qt5

Generating the recipe

appimage-builder is capable of inspecting the runtime dependencies of a given application to create a recipe for packaging it as AppImage. This can be done using the --generate argument as follows:

# run recipe generation assistant
$ appimage-builder --generate

The tool will prompt a questionnaire to gather the minimal required information to execute the application. If the a desktop entry is found in the AppDir it will be used to fill the fields but you will be able to edit all the values. Make sure of specifying the executable path properly otherwise the execution will fail.

> Basic Information :
> ? ID [Eg: com.example.app] : appimage-demo-qt5
> ? Application Name : AppImage Demo Qt5
> ? Icon : appimage-demo-qt5
> ? Version : latest
> ? Executable path relative to AppDir [usr/bin/app] : usr/bin/appimage-demo-qt5
> ? Arguments [Default: $@] : $@
> ? Update Information [Default: guess] : guess
> ? Architecture :  amd64

Once the questionnaire is completed the application will be executed. At this point ,ake sure here to test all your applications features so all the external resources it may use are accessed and detected by the tool. Once your are done testing close the application normally.

The tool will filter the accessed files, map them to deb packages and refine list to only include those packages that are not dependencies of others already listed in order to reduce the list size. Finally the recipe will be wrote in a file named AppImageBuilder.yml located in the current working directory.

Creating the AppImage

Once you have a recipe in place you can call appimage-builder to create the final AppImage. The tool will perform the following steps:

Script step

Recipes can include an optional section name script. This can be used to perform the installation of our application binaries to the AppDir. This is not created by the generator but you can edit the AppImageBuilder.yml file and add the following code before calling appimage-builder.

This step can be skip using the –skip-script argument.

script: |
    # remove any existent binaries
    rm AppDir | true

    # compile and install binaries into AppDir
    cmake . -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr
    make install DESTDIR=AppDir

Build step

This is where the major part of the job is done. The tool will proceed to gather all the dependencies and to configure the final bundle. Here are some of the actions it will perform:

  • setup an independent apt configuration to resolve dependencies and download the packages
  • download the packages
  • extract the packages into the AppDir
  • copy any other file that wasn’t found in a package (the ones listed in files > include )
  • remove excluded files (files > exclude)
  • configure the runtime environment which includes:
    • configure Qt and other frameworks/modules/libraries present in the bundle
    • setup the library and binary paths (LD_LIBRARY_PATH and PATH environment variables)
    • setup the ld-linux interpreter and deploying the custom AppRun to ensure backward compatibility
# create the AppImage
appimage-builder --recipe AppImageBuilder.yml

Note

This step can be skip by passing the argument --skip-build.

Test step

The only way of ensuring that our application will run a given GNU/Linux distribution is by testing it. The tool can make use of docker to run the AppDir that was created in the build step in different systems according to the specifications on the recipe test section.

# test section example
test:
    fedora:
      image: appimagecrafters/tests-env:fedora-30
      command: ./AppRun
      use_host_x: true
    debian:
      image: appimagecrafters/tests-env:debian-stable
      command: ./AppRun
      use_host_x: true
    arch:
      image: appimagecrafters/tests-env:archlinux-latest
      command: ./AppRun
      use_host_x: true
    centos:
      image: appimagecrafters/tests-env:centos-7
      command: ./AppRun
      use_host_x: true
    ubuntu:
      image: appimagecrafters/tests-env:ubuntu-xenial
      command: ./AppRun
      use_host_x: true

The application will be executed in each one of the systems listed above. You will have to manually verify that everything works as expected and close the application so the tests can continue.

Note

The tool will use a set of docker images that can be found here: docker test environments

Note

Downloading the docker images may take a while the first time and the application may seem idle. Please be patient or manually download the images using docker pull <image>

Warning

Docker must be installed in the system and the user must be able to use it without root permissions. Use the following snippet to allow it.

# install docker
sudo apt-get install docker.io

# give non root permissions
sudo groupadd docker
sudo usermod -aG docker $USER

# restart the your system

Note

This step can be skip by passing the argument --skip-test. You would like to use this argument when creating scripts for packaging your software using Gitlab-Ci, GitHub Actions or other build service.

AppImage step

The tool will make use of appimagetool to generate the final ApppImage file. The resulting file should be located in the current working directory.

Congratulations, you should have a working AppImage at this point!

Note

This step can be skip by passing the argument --skip-appimage.

Refining the recipe

While the --generate argument can be used to create an initial working recipe you will like to inspect and refine its contents. By example is common to find theme packages being included when those are something quite distribution specific. You can try removing those packages and run appimage-builder again (without the --generate argument) to validate that the resulting bundle is still functional. Repeat the process until you’re happy with the result.

Some libc related files may also be found in the file > include section. Those can be safely excluded most of the times but remember to test.

What’s next

The next steps for you is to learn how to do AppImage Updates and AppImage Signing. You may also want to check the recipe specification Recipe for advanced tuning.

Thanks for your interest!